In general, a heat-pump-type water heater includes a refrigerant circuit in which a compressor, a water heat exchanger, an expansion valve, and an air heat exchanger are connected by pipes in this order; and a hot water storage circuit including a tank in which water is stored, an inflow water pipe for feeding the water in the tank to the water heat exchanger, and an outflow hot water pipe for returning the water heated by the water heat exchanger to the tank. In the heat-pump-type water heater, usually, a water supply source of the water stored in the tank is tap water, well water, or the like.
Incidentally, the tap water or the well water contains components such as calcium ion, magnesium ion, and the like that cause scale (hereinafter referred to as scale components). Therefore, in a water heater, scale of calcium salt, magnesium salt, and the like is precipitated. In particular, underground water such as the well water has high concentration of the scale components compared with the tap water and has water quality that tends to cause scale. In the water heat exchanger, since the temperature of the water is high, scale is more likely to be precipitated than in other regions. When scale is precipitated and deposited on the inner surface of a pipe of the water heat exchanger, a problem occurs in that, for example, the heat transfer performance of the water heat exchanger is deteriorated or a channel of the pipe is narrowed.
For example, Patent Document 1 proposes a cooling water circulating apparatus including an electrolysis device in which one electrode pair is set in an electrolytic cell. Patent Document 1 describes that, since scale components can be removed from cooling water through electrolysis, it is possible to reduce adhesion of scale in a circulating path.
However, in the electrolysis device disclosed in Patent Document 1, removal efficiency for scale components in water is not necessarily sufficient.
Patent Document 1: WO2006/027825